THE BIRD PHOTOGRAPHER'S OUTFIT H 



using two lenses, the great size and weight of a 

 long-focus lens are drawbacks. These objections are 

 largely overcome by the use of the symmetrical 

 lenses placed in most of the long- focus boxes, or, if 

 expense be not considered, by a " convertible " lens. 



For several years I have used a "Victor" lens, 

 sold with the "Premo" long-focus camera. The 

 combined focus of the front and back lenses is seven 

 and a half inches, of either of the lenses alone, fif- 

 teen inches. The single lens therefore, the distance 

 being the same, gives an image double the size of 

 that cast by the two lenses together. 



This lens has been thoroughly tested, and many 

 of the pictures given in this book were made with it. 

 When the conditions are favorable and the subject 

 not extremely difficult it yields satisfactory results. 



The " convertible " lenses of various makers are 

 also separable, and where the rear and front lenses 

 are of different foci three focal lengths are obtain- 

 able. These lenses are of the highest grade, and 

 consequently expensive. In a bright light, or where 

 great speed is not required, they do not seem to be 

 as superior to the trade lens as the much higher 

 price would lead one to expect. But in dull days, or 

 in the shadow, or where extremely rapid exposures 

 are necessary, their superior qualities become evi- 

 dent. My experience with these convertible lenses 

 has been limited to the Zeiss Anastigmat, Series 

 VII a, of which I am now using a No. 10 with a 

 combined focus of eight inches, the front and rear 

 lenses both having a focal length of fourteen inches. 

 This combination is preferred to one in which the 

 component lenses are of different foci, because of the 



